A throttle device wherein throttle valves disposed in an air-intake passage of a throttle body are electrically driven by a motor is already known. A body of the motor is housed in a motor casing, and the throttle body and the motor casing are formed as a single piece.
Proposed is the art of improving vibration resistance of such a body of the motor by fixing its front and rear ends in its radial direction (Both-end supporting structure). The following mechanisms for holding the output shaft and the rear end (an end opposite to the output-shaft side) of such a motor are disclosed.
According to Japanese Patent Laid-Open Nos. 2002-339766 and H10-252510, the rear end of the motor is held by adding components to the rear end of such a motor.
To put it more concretely, according to Japanese Patent Laid-Open No. 2002-339766, a washer is used to hold the rear end of a motor. The washer is a ring of a plate spring. The washer has an inner edge (the plate spring) which is flexible in an axial direction by making slits in a radial direction thereof. The washer is press-fitted into a position close an inner bottom (a deep recess position) of the motor casing in advance of inserting the motor into the motor casing. Then, when the motor is inserted into the motor casing, the rear end side portion of the motor is inserted into inner circumference of the washer, causing the inner cut zone of the washer to bend backward. Thus, the rear end of the motor is held in its radial directions by the washer.
On the other hand, according to Japanese Patent Laid-Open No. H10-252510, the rear end of a motor is inserted into an elastic O-ring and the motor with the elastic O-ring is inserted into the motor casing. Thus, the rear end of the motor is held in its radial directions by the elastic O-ring in the motor casing.
In the case of the former prior art, when the motor is inserted into the motor, casing to bend the inner cut zone of the washer backward. During such motor insertion process, the outside of the motor body (yoke) may be scraped by the inner edge of the washer, and metal scraps may be produced. In addition, when inserting the motor into the motor casing, the motor may be inserted having dislingnment and held in such a state because there is no means of aligning the center of the rear end of the motor. The disalignment of the center line of the motor with the center line of the motor casing means the disalignment of the motor's driving gears with a pinion gear and an intermediate gear and causes an error in mounting the motor.
In the case of the latter prior art, when the motor with the elastic O-ring is inserted into the motor casing, the elastic O-ring may be distorted or damaged.
The object of the present invention is to provide a throttle device with a motor, which is free from the above problems and of relatively simple construction.